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Enrichment of ammonium in the future ocean threatens diatom productivity
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  • Pearse James Buchanan,
  • Juan J Pierella Karlusich,
  • Robyn Elizabeth Tuerena,
  • Roxana Shafiee,
  • Malcolm Woodward,
  • Chris Bowler,
  • Alessandro Tagliabue
Pearse James Buchanan

Corresponding Author:[email protected]

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Juan J Pierella Karlusich
FAS Division of Science, Harvard University
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Robyn Elizabeth Tuerena
Scottish Association for Marine Science
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Roxana Shafiee
Center for Environment, Harvard University
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Malcolm Woodward
Plymouth Marine Laboratory
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Chris Bowler
Institut de biologie de l'Ecole normale supérieure (IBENS), Ecole normale supérieure, CNRS, INSERM, PSL Université Paris 75005 Paris, France.
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Alessandro Tagliabue
University of Liverpool
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Diatoms are prominent eukaryotic photoautotrophs in today’s oceans. While dominant in nitrate-rich conditions, they face competitive exclusion by other phytoplankton when ammonium forms the bulk of bioavailable nitrogen. The extent to which this competitive exclusion defines diatom abundance worldwide and the consequences of potential future ammonium enrichment remain unexplored and unquantified. Here, using phytoplankton abundance proxies from the Tara Oceans dataset and an ocean-biogeochemical model, we demonstrate that ammonium enrichment reduces diatom prevalence in marine ecosystems at the global-scale. Under a high emission scenario, we anticipate 98% of the euphotic zones to experience ammonium enrichment by 2081-2100 and attribute a majority (70%) of future diatom displacement to competitive exclusion by other phytoplankton as bioavailable nitrogen supply shifts from nitrate to ammonium. Overall, the form of nitrogen emerges as a significant but previously underestimated stressor affecting diatoms and ocean ecosystems globally.
03 Apr 2024Submitted to ESS Open Archive
04 Apr 2024Published in ESS Open Archive